A clinical study, the report for which is entitled “Spinal Alignments of Male and Female Subjects in Fetal, Supine and Prone Positions While Resting on Four Different Mattresses” and dated March 1995, was conducted for Select Comfort by Dr. John Ray at the University of Memphis. The study and results were based on the generally accepted Addison’s postulation that there is the least tension in the spinal attachment muscles when a person is standing in a natural erect posture. A person’s natural erect posture was thus the baseline against which relative spinal support, alignment and comfort, were measured.
The research, conducted at the University of Memphis involved 80 subjects of a variety of ages and both sexes, resulted in complete results for 64 subjects. Two Sleep Number air mattresses, a premium innerspring mattress and a premium water mattress were used for the study. The mattresses were adjusted to be of the same firmness for part of the study, and self-adjusted by the subjects for their greatest comfort for another part of the study. The study involved sonic echoing scans and photographs of the subjects and their bodies in a natural, erect standing position and then on the mattresses being studied in the supine (lying on one’s back), fetal (lying on one’s side) and prone (lying on one’s stomach) positions. The purpose was to determine spinal alignment in these various circumstances. Study data were also collected by means of checklists completed by subjects to determine mattress preferences, comfort levels and other relevant information.
The major findings of this clinical study were that “[Sleep Number® mattresses] had less or equal average spinal deviation than the other two systems,” that “changes in pressure [for the Sleep Number mattresses] had minor effects on the changes in spinal shape,” and that “[t]here is not much difference [in the study results] in the soft and firm configurations” of Sleep Number mattresses. Dr. Ray’s conclusion was that Sleep Number mattresses “gave the best comfort and spinal alignments to the subjects tested.”